1. Field of the Invention
The present invention relates generally to a scroll type compressor. More specifically, the present invention relates to a scroll type compressor which includes an improved mechanism for transmitting reaction force applied from an orbiting scroll to the compressor housing.
2. Description of the Related Art
Conventional scroll type compressors generally include a standard structure having a two offset scroll members. Both scroll members have spiroidal or involute spiral members attached to a circular end plate. The spiroidal members are interfit and nestled with each other so that as a rotary shaft rotates one member around the other fixed member, a gas chamber is formed by the interfitting spiroidal members. During the course of the orbiting scroll's rotation, the volume and location of the gas chamber is defined by the interfitting scroll members, with the volume of gas decreasing as the rotation progresses. Gas is compressed in this manner when a constant volume of gas within the gas chamber decreases in size according to the progression of the rotating spiral member. According to the general construction of scroll type compressors, the orbiting scroll exhibits a tendency to rotate around its axis due to the rotation of the rotary shaft. It is necessary, however, to prevent the scroll from rotating around it's own axis and to keep it either horizontally or vertically in order to optimize the compressor's operation.
Japanese Examined Patent Publication No. 2-2476 discloses a compressor which includes an anti-rotation mechanism as described above. In this technology, as shown in FIG. 16, an orbiting scroll 102, interfit with a fixed scroll 100 in housing H, receives a reaction force of a compressed gas in compression chambers 106 due to the rotational force of a rotary shaft 104. The rear surface of a base plate 108 of the scroll 102 abuts against a pressure receiving wall 112, via the anti-rotation mechanism 110.
The mechanism 110 includes a movable ring 118 and a fixed ring 120 which are disposed between the base plate 108 and the wall 112, via races 114, 116, respectively (see FIG. 16). The movable ring 118 moves integrally with the scroll 102 and has a plurality of pockets 122 and 124, spaced within the circumferences of the rings 118, 120, at predetermined intervals, respectively. Rod shaped rollers 126 are horizontally supported between the associated pockets 122, 124 which are offset and facing each other.
In reaction to the rotation of rotary shaft 104, scroll member 102 and ring 118 rotate, and rollers 126 roll in the region of associate pockets 122, 124. Accordingly, the orbiting scroll 102 performs the orbital movement without itself rotating.
The diameter D of the pockets 122, 124 can be defined by the following formula: EQU D=d+r
where d is the diameter of the roller 126, and r is the radius of the orbiting scroll 102. Therefore, the diameter of the rollers 126 and the radius r of the orbiting scroll determine and control the diameter of the pockets 122 and 124.
End surfaces of the rollers 126 are slidably contacted with the races 114 and 116. The compression reaction force applied to the orbiting scroll is transmitted to wall 112, via the rollers 126. To improve upon the rigidity of the compressor, either the diameter or the actual numbers of rollers 126 should be increased. The enlarged pockets require the orbiting ring 118 and the fixed ring 120 to be wider. However widening the rings 118, 120 causes an increase of the overall sizing of the compressor and such a large compressor is not desirable for mounting in a vehicle.
To increase the ability for transmitting the compression reaction force without increasing the size of the compressor, it is necessary to increase the number of the rollers 126. However, the increase of the number of the rollers 126 increases the number of the pockets 122, 124. The increase of the number of the pockets 122, 124 which require a high precision process leads to longer processing time and higher manufacturing cost.